Abstract: An investigation of the effect of a single air chamber on the propagation of a pressure surge in a line is carried out. The pressure surge is generated by rapid closure of a downstream valve. Both a distributed parameter wave analysis and a lumped parameter slug flow analysis are formulated to describe the transient flow situation. It is shown that short term effects, which are not predicted by a lumped parameter analysis, may be important, and that the magnitude of the short term surge may be many times greater than that predicted by a lumped parameter analysis. It is further shown that an optimum design of an air chamber is possible, and this is dependent on short term effects. Experiments are conducted which are in close agreement with predicted results. It is pointed out that the performance of an air chamber must be evaluated relative to a specific application and that an accurate transient analysis is necessary and can be accomplished utilizing the approach described herein.